Voice Extensible Markup Language (VoiceXML) is a markup language for creating voice user interfaces that use automatic speech recognition and text-to-speech synthesis and is described, for example, at http://www.voicexml.org, http://www.vxml.org, http://www.w3.org/TR/voicexml20/ and elsewhere. VoiceXML has tags that instruct the voice browser to provide speech synthesis, automatic speech recognition, dialog management, and audio playback.
Proposals, such as Google VoiceSearch, exist for searching conventional web sites through voice.